WASHINGTON -- A Republican senator asserted Tuesday during a rancorous floor debate that President Barack Obama's health care overhaul will shorten the lives of America's seniors by cutting Medicare.

"I have a message for you: You're going to die sooner," said Sen. Tom Coburn, R-Okla., an obstetrician-turned-lawmaker.

A senior Democrat decried such comments as scare tactics designed to kill legislation that he said would improve some benefits for seniors. At times, the debate recalled the raw charges and countercharges of the summer's town hall meetings.

"I hate to say it ... these are scare tactics," Baucus said. "Sometimes you've got to call a spade a spade." The Senate was debating an amendment by Sen. John McCain, R-Ariz., that would strip from the bill more than $400 billion in Medicare cuts to home health providers, hospitals, hospices and others.

Polls show that seniors are concerned that expanding coverage for the uninsured will come at their expense. Earlier this year, former GOP vice presidential candidate Sarah Palin warned of "death panels" that would deny coverage to frail seniors -- a charge that was widely debunked. Medicare spending actually would keep growing under the Democrats' legislation, albeit at a slower rate.

Despite the partisan sparring over Medicare, the first health care amendment offered was bipartisan, a measure to increase preventive care for women co-sponsored by Sens. Barbara Mikulski, D-Md., and Olympia Snowe, R-Maine. Snowe was the only Senate Republican to vote in favor of Democrats' health care legislation in committee.

Their amendment would give the Health and Human Services secretary authority to require health plans to cover additional preventive services for women and was inspired in part by controversial recommendations last month that women undergo fewer mammograms and Pap smears to test for cancer. Republicans seized on those recommendations as early signs of rationing of care they say would happen under the Democrats' 10-year, nearly $1 trillion health bill.

The Mikulski amendment "makes clear, no matter what the Republicans claim, that the decision whether or when to get a mammogram should be left up to the patient and the doctor," said Senate Majority Leader Harry Reid, D-Nev. "That decision should not be made by some bureaucrat, a member of Congress or someone they've never met."

However the amendment doesn't specifically address mammograms or spell out what additional services would be covered, leaving that to the discretion of the HHS secretary. The Congressional Budget Office said the amendment would cost $940 million over a decade.

Last month, a government-appointed but independent panel of doctors and scientists said women generally should begin routine mammograms in their 50s, rather than their 40s. Then, in an apparent coincidence, the American College of Obstetricians and Gynecologists said most women in their 20s can have a Pap test every two years -- instead of annually -- to catch slow-growing cervical cancer.

Neither the task force, which provides advice to government officials who may or may not act on it, nor the doctor's group sets federal policy.

But the recommendations could not have come at a worse time for majority Democrats, especially Senate leaders trying to hold together the 60 votes required to advance the health care overhaul.

"We know that some in Washington have wanted government-run health care for years. And it's hard to escape the conclusion that these same people saw the current economic crisis as their moment," said Minority Leader Mitch McConnell, R-Ky. "Earlier this year, some in the administration said that a crisis is a terrible thing to waste. Americans are hoping this bill isn't what they meant. But they're concerned it is."

The legislative struggle is expected to last for weeks in a test that pits GOP senators determined not to give ground against Senate Democrats intent on delivering on Obama's signature issue.

Dozens of amendments are likely to be offered, with the measures seemingly designed as much to court a skeptical public as to reshape Reid's 2,074-page bill.

The Congressional Budget Office has estimated that 31 million uninsured individuals would receive insurance if the bill were enacted, many of them assisted by federal subsidies. The legislation would be paid for through a combination of cuts in projected Medicare payments, a payroll tax on the wealthy and taxes on drug makers, medical device manufacturers, owners of high-cost insurance and others.